This station is located in the middle of Kilmarnock. It is a four platform station with two bay platforms at the north end and two mainline platforms. There are three tracks between the main platforms. The bay platforms and northbound (down) platform are canopied.
The original 1843 station was substantially rebuilt in 1873-78, following the opening of the joint line via Barrhead. (See Kilmarnock [1st] for the earlier version of the station.) The main building is on the northbound platform. It is built in red sandstone. The building features a tall tower at the east end. This features round windows on the top floor, curiously not fitted with clocks (although there is a large clock in the grounds). A double ramp runs up to the station, passing the car park. At low level is a castellated building, the entry to an underpass under the station and former ticket office. The architect was probably Andrew Galloway, engineer of the Glasgow and South Western Railway.
The original 1843 down side station building survived until the 1990s, just to the north west of its replacement.
The 1870s reconstruction of the station remains largely intact, although the south end bay platform, west side, and east face of the island platform are now out of use. The northbound platform and bay platforms area is canopied.
Signal boxes opened at the north and south ends of the station in 1873. The north box was on the south side of Kilmarnock Junction. The south box was at the east end of the station, just west of Kilmarnock Water Viaduct.
In 1890 the north box was replaced with the first No 1 box. The south box was renamed to become the first No 2 box. The first No 3 box had opened in 1889 - this was on the north side of the station, between No 1 and No 2. It controlled access to single ended sidings to the west and locomotive shed and turntable to the east.
With the opening of a new No 1 box at Bonnyton and Kilmarnock Goods Junction in 1926 there was a further renaming. The north box at Kilmarnock Junction, the first No 1, became No 2. The south box, the first No 2, became No 3. The middle box, the first No 3, became No 4.
The middle box, No 4, closed in 1966. The north, No 2, and south, No 3, boxes closed in 1976 when replaced by Kilmarnock Power Box.
The original building was in Georgian style. It was thought to be by James Miller and was demolished despite being listed. It was reminiscent of his work at Haymarket.
Kilmarnock Station Railway Heritage Trust - Storm in a Teacup Cafe is based in the station building.